Structure of Azotobacter ferredoxin in tetragonal crystal: a. Preparation of 2.8 A Fourier map based on pt derivative alone; b. Interpretation of 2.8 A map on the departmental MMS-X Graphics Display System; c. Inclusion of Fe anomalous scattering measurements in phase calculations; d. Search for additional heavy atom derivatives; e. Extension of native data to 2.0 A and refinement of the structure on the MMS-X system; f. Data collection on the protein crystals in the fully oxidized and fully reduced states. Structure of ferredoxin in the triclinic crystal: a. Data collection on native crystal; b. Structure analysis by molecular replacement methods. Structure of cytochrome c5: a. Search for heavy atom derivatives of triclinic crystal from; b. Application of molecular replacement methods using 2.5 A native data. Crystallization of flavodoxin to improve quality of crystals.